The Contour > Expand Contour command will use the selected contours as a trajectory for drawing parallel contours, one on either side of the selection:

Source open contour

Path is expanded with parallel contour

To use this operation, first select the contours you want to expand. Note that all contours that have at least one node selected will be processed. If nothing is selected, the expansion will be applied to whole element contour. Select the Contour > Expand Contour command in the menu. You will see a dialog box that allows you to select options:

Here you can set the Distance between parallel contours, and the way you would like corners and ends of open counters to be treated:

Flat contour ends vs. round ends

When you finish selecting options, click on OK to expand the selected contours.